1. Field of the Invention
The present invention relates to a process for producing an artificial bone model. More particularly, the present invention relates to an artificial bone model which can three-dimensionally reproduce steric shapes of natural bones such as bones in the human body precisely and accurately and exhibits the property for cutting closely similar to that of natural bones. The present invention further relates to an artificial bone model produced by the process and a use of the artificial bone model for educational training or for studying a plan for curing before a surgical operation.
2. Description of Related Art
Medical treatments accompanied with cutting of bones such as recovery of a skull having defect or deformation, treatments of auditory organs having a complicated structure of bones, surgical treatments of necrosis of caput ossis femoris and treatments of various types of complicated fracture have been conducted in wide areas such as the orthopedics, the brain surgery, the pectoral surgery, the oral surgery, the otorhinolarygology, the plastic surgery and the veterinary surgery. However, the opportunity for educational training of doctors skilled in the surgical treatments accompanied with cutting of bones is not frequent. Heretofore, as the material used for education, training and experiment in the medical field, models prepared by visually imitating the appearance of bones taken from remains of animals and human beings in accordance with artistic methods such as carving and cutting using paper, synthetic resins, wood and gypsum have generally been used. In limited cases, real bones are provided as postmortem specimens by the favor of a deceased person or the bereaved. However, it is actually difficult to obtain bones for educational, training and experimental purposes.
When a portion of a bone has a damage due to a disease or an accident, the bone is spontaneously recovered when the width of the damage is 5 mm or smaller. However, when the damage in a bone exceeds 5 mm, auto-transplantation of the bone is conducted taking a portion of a bone of the hip or a leg of the patient. However, since the size of the bone which can be taken is limited and the load to the body of the patient is great due to cutting of a healthy portion of a bone, various artificial bones have been developed and utilized. For example, as the artificial bone which is made of biologically active materials and organic polymers, has a great mechanical strength and exhibits a great biological activity, an artificial bone which is made of 30 to 90% by weight of glass powder containing CaO and SiO2 as the main component and 10 to 70% by weight of a copolymer of 2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)-phenyl]propane and triethylene glycol dimethacrylate or the like is proposed (Japanese Patent Application Laid-Open No. Heisei 6(1994)-154305, page 2). As the composite material for artificial bones exhibiting excellent mechanical properties and biological compatibility, a composite material made of titanium and hydroxyapatite prepared in accordance with the metal powder injection molding process is reported (Hideo Furuzawa, Yasuhiro Kataoka and Koichi Nagata, Aichi-ken Kogyo-Gijutu Center Kenkyu Hokoku (Research Reports of the Center fo Industrial Technology of Aichi Prefecture), No. 37, 2001). An artificial bone made of titanium in accordance with the laser sintering rapid prototyping process is also reported as the artificial bone which is custom-made in accordance with the condition of the individual patient.
The above artificial bones are embedded in the living body by the surgical operation and supplements the natural bones. The properties are focused on the strength and the compatibility with the body and other properties such as the property for cutting are, in general, far different from those of natural bones. It is not necessary that the artificial bone embedded in the living body has completely the same shape as that of the natural bone since it is sufficient that the artificial bone can functionally supplement the natural bone. In general, an artificial bone has a simplified shape than that of the natural bone. Therefore, an artificial bone prepared for embedding into the living body is not suitable for the training for surgical operations.
For a shaped model for medical uses, the model should have the same shape as the natural bone including the detailed structures and have the real shape enabling manual examination of the three-dimensional structure which cannot be seen directly from the outside. A technology in which data of the steric shape of the human body are supplied to an apparatus for optically forming a shape and an artificial bone model is prepared by curing a photocurable liquid resin. (Kazuyuki Takahashi, Preprints of the 23rd Rapid Prototyping Symposium, page 31, 2002). The shape including detailed structures can be reproduced accurately when a photocurable liquid resin is used. However, since the article which are being prepared by the process cannot stand by itself during the preparation, it is necessary that a support called a supporting structure be added during the preparation and be removed manually after the preparation is completed. The cured product of the photocurable resin exhibits the property for cutting far different from that of the natural bone and is not suitable for training for the operation of cutting bones.
It is attempted that three-dimensional data are reconstructed from X-ray CT images and an artificial bone model is visually observed three-dimensionally on a display. In accordance with this method, many images of sections of the artificial bone model cut at desired portions can be displayed, and various simulations can be conducted with examination of the shapes before the operation. However, the effect of the examination on the display is limited, and it is most desirable that a plan for curing is made before the operation using a steric artificial bone model having the same shape as that of the natural bone.